1. Field of the Invention
The present invention relates to a solid-state image capturing device for performing photoelectric conversions on and capturing image light from a subject, a camera module, and an electronic information device, such as a digital camera (e.g., digital video camera and digital still camera), an image input camera (e.g., car-equipped monitoring camera), a scanner, a facsimile machine, and a camera-equipped cell phone device, using the solid-state image capturing device as an image input device in an image capturing section.
2. Description of the Related Art
A cross sectional structure and method for manufacturing a conventional solid-state image capturing device described above will be described with reference to FIG. 18.
FIG. 18 is a cross sectional view schematically illustrating an exemplary essential structure of the conventional solid-state image capturing device.
As illustrated in FIG. 18, when a conventional solid-state image capturing device 100 is manufactured, a plurality of photodiodes (light receiving sections) 102 are first formed by impurity ion implantation in an image capturing area of a silicon substrate 101.
Next, a gate insulation film 103 is formed on the silicon substrate 101 by heat treatment in an oxygen atmosphere, and subsequently, a gate electrode 104 for transferring a signal charge generated by photoelectric conversions at the photodiode 102 towards the side of an output circuit is formed by a decompression CVD method for poly-silicon and the like.
Subsequently, a light shielding film (not shown) is formed with a material such as tungsten in an area other than the photodiode where light above the gate electrode 104 enters, and an interlayer insulation film 105, such as a BPSG film (which is a silicon oxide film including phosphorus and boron), is formed. A reflow process (heat treatment) is performed to eliminate the difference in the level on the surface so as to planarize it.
Further, although not shown herein, a metal layer, which will be a wiring of a peripheral circuit and a gate electrode, is formed on the interlayer insulation film 105 by a single layer of a material, such as Al.Al—Si.Al—Cu, or a multilayer film of such material and TiN.Ti.TiW and the like. At this stage, a plurality of electrode pads 106 for inputting and outputting a signal with the exterior of the device are simultaneously formed in the outer circumference edge section of the solid-state image capturing device 100 (device chip or solid-state image capturing chip).
Although not shown herein, a passivation film is formed with a material such as plasma SiN (P-SiN) and plasma SiON (P-SiON) above a metal layer that will be a wiring of a peripheral circuit and a gate electrode, and subsequently, a passivation film is removed above the electrode pad. These portions, so far, form the portions performing solid-state image capturing functions and all the material used so far to form films are inorganic materials.
The step subsequent to this is the formation of optical system portions for separating colors and focusing light of image capturing elements, and almost all of them are formed with organic materials.
First, a planarization film 107 for planarizing the foundation for forming a color filter is formed by spin-coating a transparent organic material, and the planarization film 107 above the electrode pad 106 is etched and removed so as to expose the electrode pad 106 again.
A color filter 108 is formed above the electrode pad 106 and the planarization film 107 by photolithography process. The color filter 108 will have a color arrangement of R, G and B, such as the Bayer arrangement, when the plurality of color filters 108 are the primary colors. The color filter 108 will have a color arrangement of Cy (cyan), Mg (magenta) and Ye (yellow) when the plurality of color filters 108 are the complementary colors. In the photolithography process, the exposed surface of the electrode pad 106 may be exposed to a developing solution or a material of the color filter 108 may appear on the exposed surface as a residue. Note that, although filters formed in the color filters of complementary colors are in three colors of Cy (cyan), Mg (magenta) and Ye (yellow), the filter arrangement is a four color arrangement including Gr (green), which is formed by overlapping the Cy (cyan) and Ye (yellow).
Next, a planarization film 109 as a foundation layer for forming a microlens 110 is formed by spin-coating a transparent organic material on the color filter 108, and the planarization film 109 above the electrode pad 106 is etched and removed so as to expose the electrode pad 106 again.
Subsequently, the microlens 110 for focusing incident light on the photodiode 102 is formed by the photolithography process and baking process of a transparent organic film material.
In this case, the electrode pad 106 may be exposed to a developing solution by the photolithography process in a state with the exposed electrode pad 106, and a residue of the color filter 108 may appear above the electrode pad 106, which will result in a poor wire bonding to the electrode pad 106. Although the roughness and the residue of the electrode pad 106 can be removed by plasma ashing, an organic material such as a microlens material is also exposed to plasma ashing, resulting in roughness of the surface of the microlens 110 itself and damaging it.
For such a damage to the microlens 110, a protection layer 111, which is formed by an organic or inorganic SOG film (Spin on Glass), CVD-SiO2 film and the like, is formed, and an opening is formed by the photolithography process of the protection layer 111, and subsequently an ashing process is performed in a state having a resistor subsequent to the removal of a resist.
For this problem, Reference 1 discloses a way to further add an improvement to the conventional method described above. The conventional method described above uses a method for removing a film above the electrode pad 106 every time a film of an organic material is formed. However, the film above the electrode pad 106 is not removed and left intact. Subsequent to the formation up to and including the microlens 110, an opening is resist-patterned above the electrode pad 106, and the organic film is totally etched and removed at once above the electrode pad 106 by dry etching such as O2/CF4 plasma. The problem described above can be solved by this method.
In recent image capturing devices, the protection film 111 above the microlens 110 is substantially formed not for the function of the protection film 111 provided against the damage of the microlens 110 but for the function of a reflection preventing film for preventing the reflection of light that enters the microlens 110.
Reference 2 discloses this reflection preventing film. In Reference 2, a film with a material having a lower refractive index than a microlens material (transparent organic material with refractive index of 1.6) is laminated above the microlens so as to prevent reflection on the microlens surface. As a result, light focused on the photodiode can be increased. Conventionally, such reflection preventing film is formed by laminating a silicon oxide film (SiO2) with a refractive index of 1.45 by the CVD method and the like.    Reference 1: Japanese Laid-Open Publication No. 2006-351761    Reference 2: Japanese Laid-Open Publication No. 4-223371